M1 L2: Mitosis and Meiosis Flashcards
what is genetic continuity
the process of passing genetic material onto future generations so that the offspring resemble the parents
what’s the role of the plasma membrane? what cells have one?
separates the inside of the cell from the environment. all cells
what’s the role of the cell wall? what cells have one?
provide more structural support. plant cells
what’s the role of the glycocalyx? what cells have one?
outer layer of glycoproteins and polysaccharides that acts as the cell’s ID. many animal cells
What is the cytoplasm? what does it contain?
everything outside the nucleus, contains organelles and cytosol (liquid that also contains free ribosomes), structures that make up the cytoskeleton (microtubules from tubulin, microfilaments from actin)
what are the two parts of the ER? what does each do?
rough has ribosomes on the surface, site of translation and protein synthesis
smooth does not have ribosomes, site of phospholipid and fatty acid synthesis
what’s the role of mitochondria? what’s special about this organelle?
site of oxidative phosphorylation and ATP synthesis
they have their own DNA (mtDNA), replicate themselves, transcribe and translate their own proteins, result of endosymbiosis
what’s the role of chloroplasts? what’s special about this organelle?
capture sunlight for photosynthesis
have their own DNA (cpDNA), replicate themselves, transcribe and translate their own proteins, result of endosymbiosis
Characteristics of prokaryotes
chromosome is in nucleoid region, no nucleus, no membrane bound organelles, DNA less compacted and less associated with proteins, circular chromosomes
Characteristics of eukaryotes
nucleus, membrane bound organelles, DNA more compacted and more associated with proteins, linear chromosomes
whats the nucleolus
inside nucleus, where rRNA is made, ribosome assembly starts
what parts of DNA contain repeats of rRNA genes?
nucleolar organizer region (NOR)
what’s chromatin
fibers of DNA and proteins that make up chromosomes
what’s the centromere?
constricted part of chromosome, specialized sequence where kinetochore binds, divides chromosome into p and q arms, allows us to qualify chromosomes in categories
categories of chromosomes / centromere locations
1) metacentric: centromere in middle
2) submetacentric: near middle
3) acrocentric: near end
4) telocentric: at end
what are homologous pairs
pairs of chromosomes with the same genes, possible different alleles
what’s biparental inheritance?
offspring get one chromosome from each parent
dwhat’s the difference between sister chromatics and homologous pairs?
sister chromatids are the product of DNA replication, identical
homologs are the same chromosome but from different parents, same genes but might not have identical alleles
does chromosome number correlate with genome size or complexity? how do we know?
NO. fruit flies have 4 chromosomes, yeast has 16
what is karyokinesis?
separation of genetic material into daughter cells
what’s cytokinesis?
separation of organelles and membranes into daughter cells
Purpose of mitosis?
asexual reproduction in budding organisms, growth from zygote to adult for multicellular organisms
what are the phases of the cell cycle
interphase (G1/G0, S, G2) and mitosis (prophase, prometaphase, metaphase, anaphase, telophase)
describe the subphases of interpahse. are chromosomes visible?
G1- cell grows, may go into G0 (nondividing but metabolically active)
S- cell replicates DNA
G2- cell grows, prepares for mitosis
CHROMOSOMES NOT VISIBLE
describe mitosis prophase
centrioles (organelles made of tubulin) go to centrosomes on opposite ends of cell most plants/fungi don’t have centrioles
nuclear envelope breaks down
chromosomes condense, form sister chromatids (sister arms held together with cohesin)
describe mitosis prometaphase
centrioles reach opposite poles, produce spindle fibers from centrosome
kinetochore binds centromere (# kinetochore attachments/chromosome varies across organisms)
spindle fibers attach to kinetochore
separase degrades cohesin except at centromere (shugoshin protects cohesin)
sister chromatids migrate to metaphase plate
what are spindle fibers made of? what are their 3 functions?
microtubules made of tubulin.
1) chromosome movement
2) stabilize cell during division
3) cell elongation before cytokinesis
describe mitosis metaphase
chromosomes are lined up on metaphase plate
describe mitosis anaphase
sister chromatid disjunction into daughter chromosomes via molecular motor proteins (use ATP to shorten spindle fibers)
shugoshin and cohesin break down
describe mitosis telophase
full set of chromosomes on each end of cell
cytokinesis (animal cells: form cell furrow by constricting cell membrane along metaphse plate) (plant cells: cell plate forms, site of new cell wall)
reform nuclear envelope
decondense chromosomes
what proteins regulate the cell cycle
cyclins are produced at different points in the cell cycle
cyclins bind to and activate cyclin dependent kinases
CDKs phosphorylate other proteins
what are the 3 checkpoints in the cell cycle
G1/S - big enough to replicate DNA? DNA damage?
G2/M - DNA replication finished? Replicated correctly?
M- spindle fibers formed and fully attached to kinetochores?
can haploids and diploids sporulate?
sporulation = meiosis, only diploids can, both can do asexual reproduction with mitosis
purpose of meiosis?
go from 2N to N to maintain genetic continuity (not make a 4N zygote)
what’s crossing over?
homologs exchanging genetic material in meiosis I
how to tell when ploidy has been reduced?
count centromeres
describe the 5 steps of prophase I
chromosomes already replicated
1) leptonema: chromatin condenses (chromomeres: localized condensations resemble beads), chromosomes become visible, start looking for homolog
2) zygonema: synaptonemal protein complex forms between homologs, closely associated homologs = a bivalent
3) pachynema: homologs get closer (synapsis), crossing over, double structure of each homolog in the bivalent is clear = a tetrad
4) diplonema: homologs separate slightly, still joined at chiasmata (site of recombination)
5) diakinesis: terminalization (chiasmata move to ends of chromosomes), nucleolus and nuclear envelope break down, spindle fibers attach to kinetochores on homolog centromeres
how do X and Y chromosomes pair?
have pseudoautosomal regions (PAR)
describe the rest of meiosis I. What are the analogous structures in mitosis?
metaphase I: recombined tetrads (pair of homologs) line up on metaphase plate (homologs are side by side but would be end to end in mitosis)
anaphase I: recombined homologs are pulled apart (disjunction) (would be sister chromatids in mitosis), form dyads
telophase I: cytokinesis, separate into 2 daughter cells, sometimes form nuclear envelope
prophase II: dyads (nonsister chromatids) still condensed
metaphase II: dyads line up end to end
anaphase II: nonsister chromatids of dyads get pulled apart
telophase II: cytokinesis, nuclear envelope forms
molecular basis for independent assortment?
SBS arrangement of bivalents in tetrads is random in metaphase I
minimum possible genetic combinations 2 organisms can produce in their offspring?
(2^n)^2
2 (maternal/paternal allele) ^n (for # of unique chromosomes) ^2 (both parents contribute)
describe meiosis in males
spermatogenesis: diploid spermatagonium grows into primary spermatocyte, meiosis I makes 2 secondary spermatocytes, meiosis II makes 4 spermatids, gain mobility and become mature spermatozoa
*cytoplasm divides equally
describe meiosis in females
oogenesis: diploid oogonium grows into primary oocyte, meiosis I makes a secondary oocyte and polar body, meiosis II makes an ootid and another polar body, grows into ovum
*cytoplasm does not divide equally
are all genes DNA?
no, some viruses use RNA as genetic material. everything else uses DNA
